In general, methacrylic resin compositions containing a cross linked elastic body excellent in transparency, weather resistance, hardness and impact resistance are used in the state that an ultraviolet absorber is mixed therewith. In particular, in the case of using a methacrylic resin composition as described above as a film, it is necessary to add an ultraviolet absorber thereto in a larger amount as the thickness of the film is made smaller.
For this reason, in the case of forming the composition into a film by extrusion molding or some other methods, there are caused problems, such as the clogging of a vent in the extruder, the adhesion of a gum to the T die, and the whitening of the cooling roll. Moreover, in the case that it is necessary that the ultraviolet absorber is added in a far larger amount, the roughening of the surface of the film, the bleeding-out thereof to the film surface, and other problems are caused.
Even if a great amount of an ultraviolet absorber can be added to a methacrylic resin composition, the absorbent partially volatilizes when the composition is subjected to extrusion molding since ordinary ultraviolet absorbers are generally poor in compatibility with methacrylic resin and have a low molecular weight. As a result, the film made of the composition cannot exert ultraviolet ray shielding performance. Furthermore, the ultraviolet absorber has a problem that the ultraviolet ray shielding effectiveness lowers with the passage of time since the ultraviolet absorber is dispersed from the methacrylic resin composition when the composition is used for a long term.
In order to solve these problems, known is generally a method of selecting a specific ultraviolet absorber and adding the absorber. However, according to the method of adding a specific ultraviolet absorber merely, from the resultant film, the added ultraviolet absorber bleeds out when the film is immersed in hot water or kept outdoors; thus, problems such that the ultraviolet rays shielding performance deteriorates and the film whitens, and other problems are unsolved.
On the other hand, suggested are methods of copolymerizing a specific monomer having ultraviolet absorbability with a methacrylic resin (Patent Documents 1 to 4). However, films obtained from these methods do not satisfy flex cracking resistance, flex whitening resistance, formability (formability into a thinner film), or others.
Patent Document 1: JP-A-60-38411
Patent Document 2: JP-A-05-255447
Patent Document 3: JP-A-09-194542
Patent Document 4: JP-A-08-319326